Geographic origin of dust samples identified using fungi-a new method
Pollen; the main material used in the study of palynology.
Several archeological and paleoecological studies utilize tiny particles to acquire insight regarding something’s geographical origin, or to learn about the composition of an ancient ecosystem. Palynology is the study of plant pollen, spores and microscopic plankton organisms. In most cases, pollen is used. In 2007, pollen data was utilized to see how early humans during the Holocene (hunter-gatherers) interacted with their local ecosystem. Several species were found to be correlated with settlements, showing early humans clearly altered their surrounding habitats. Although using pollen has been shown to be quite useful, identifying pollen is extremely time consuming, and requires an enormous amount of knowledge about plant species along with their distributions. A new method utilizing fungal spores may speed this process up, make it cheaper, and increase geographic certainty.
Eutypa lata distribution. Grantham et al. 2015.
Teratosphaeria microspora distribution. Grantham et al. 2015.
Neal S. Grantham and his team of nine scientists set out to analyze nearly 1,000 dust samples distributed across the United States. Instead of looking at the organic particle’s morphology, they used a high-throughput sequencing method to explore the fungal diversity within these dust samples. With these analyses, over 40,000 fungal taxa were quantified! Many of these fungi identified have a unique geographic distribution; a key component to sufficiently locating where each sample came from. If you look at the maps above, you can see the narrow distribution of a single species of fungus, Eutypa lata. Other species, like Teratosphaeria microspora, have an enormous distribution, and are less helpful in locale identification. These represent just two species of fungus though, and given that each dust sample contained an average of 727 fungal taxa, one can start to see how effective this method actually is at locating a samples geographic origin.
By means of these fungal genomic data paired with some intense model algorithms, Neal and his team were able to predict the general location of the dust samples. To predict the location of a single dust sample even with an error of 229.3 km is remarkable in itself, especially with the gargantuan scale of the United States. This new method really does have some impressive applications, but still, is not perfect.
Just one of the several statistical models used in this study... Grantham et al. 2015.
The DNA molecule does have a half-life of 521 years, which means that it should last 6.8 million years. Now, environmental DNA (eDNA) is bombarded by the elements, experiencing countless changes in temperature and moisture, which ultimately breaks down this fundamental organic molecule much faster than its half-life suggests. The most ancient eDNA isolated that I have found throughout the scientific literature comes from Siberian permafrost, where conditions stay most consistent. Even so, these samples were dated at 400,000 years old. DNA in dust that is not frozen will not last this long. Still, since humans are the new kids on the block, the dust riddled articles of clothing found that our ancestors once wore can still yield geographic data using these new methods. Fungi living from the forest floor can help us locate the region a few dust particles came from. Future studies using these forest floor inhabitants just might inform us about the ecology of our ancestors.